1. Field Of The Invention
This invention relates to a closed-loop system for monitoring and maintaining the temperature and humidity of air within a holding cabinet. In particular, the invention relates to a system for use in a heat and humidity controlled cabinet for holding food products which monitors and adjusts air temperature and humidity to maintain substantially constant levels despite the opening and closing of the cabinet access.
2. Description Of The Related Art
There are presently numerous cabinets for holding food products or other items in a temperature and humidity controlled state. These cabinets, however, suffer from a common shortcoming. When the cabinets are opened to insert additional food products or other items or to remove such products or items from the cabinets, heat and humidity are lost. Unless the lost heat and humidity can be restored, the items stored in the cabinets may cool or dry out, or both.
Previously, various methods have been attempted to maintain heat and humidity within such cabinets. For example, pans of water have been placed in the cabinets and allowed to evaporate naturally in an attempt to maintain humidity. Despite its simplicity, this method has not been completely successful. Natural evaporation cannot quickly compensate for humidity losses. Further, while humidity is naturally increasing, items stored in the cabinets are subject to the drying effect of heat. Moreover, because natural evaporation will be effected by the temperature within the cabinet, the rate of humidity adjustment may fluctuate with temperature changes, but humidity adjustments will probably lag behind such temperature changes.
Systems have been developed by which the heat and humidity levels of air within a cabinet could be more closely controlled. Air may be heated by passing it over or across various types of heating elements. Air may also be passed over or through water in order to raise the humidity of the air. Despite these improvements, the existing systems remain unable to precisely adjust for losses of heat or humidity due to disruptions to the cabinet environment, such as opening and closing the cabinet access and added or removing food products or other items. Further, the addition of heating elements and humidity generating means can create additional problems. If heat or humidity rise too quickly, the air within the cabinets could become overheated or too moist. Such uncontrolled fluctuations in heat and humidity can be detrimental to food products or other items stored within the cabinets.
Cabinets commonly are equipped with thermostats in an attempt to control the heat of the air circulating within the cabinets. By controlling the air temperature, however, the humidity of the air can also be affected. Nevertheless, such controls alone do not provide adequate control of the humidity within the cabinet. Moreover, a thermostat or manual potentiometer may not maintain temperature and humidity within predetermined parameters. Generally, such devices only cause the heating elements to heat the air when the air temperature falls below a set value.
These problems are readily solved by the present invention. Air temperature and humidity can be maintained within predetermined parameters despite the repeated opening and closing of the access to the cabinet and the addition or removal of food products or other items. The present invention not only can monitor both air temperature and humidity, but can react to and adjust for changes in either, or both, of them.